What was found
THE CREW REPORTED THAT THE HYDRAULIC PRESSURE WAS READING HIGH IN FLIGHT. WHEN THE HYDRAULIC PRESSURE DROPPED TO ZERO THE CREW CLOSED THE EMERGENCY DUMP VALVE. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT WAS DIVERTED TO KSAN DUE TO THE HIGHER RUNWAY LENGTH IN THE EVENT THAT THE EMERGENCY BRAKES WOULD HAVE TO BE USED. WHEN THE AIRCRAFT WAS LANDED, THE USE OF NORMAL BRAKES RESULTED IN HYDRAULIC PRESSURE FLUCTUATIONS. MAINTENANCE REPLACED THE NR 2 ENGINE DRIVEN HYDRAULIC PUMP. NEW HYDRAULIC PACK FILTERS WERE INSTALLED FOR THE LEFT AND RIGHT POSITIONS. GROUND RUN OPERATIONAL CHECKS WERE NORMAL. THE AIRCRAFT WAS RETURNED TO SERVICE.